In recent years, horizontal directional drilling techniques combined with hydraulic fracturing has enabled the previously thought impossible harvest of natural gas resources from impermeable rock and shale formations. Hydraulic fracturing is a process whereby a fluid, typically water, brine, emulsions of oil and water, or liquid-gas foams, are injected into the ground at high pressure to stimulate, create cracks and fracture the rock or shale formation to increase the flow and recovery of oil and gas. Sand or other proppant material is typically injected to prop open the cracks in the formation, increase permeability, and allow the oil or gas to flow to the well. Vertical and horizontal rotary drilling methods are typically treated with multiple fracturing jobs to create numerous artificial fractures in the formation and recover more oil and gas.
At the wellhead, the equipment for hydraulic fracturing generally includes multiple fluid tanks, chemical blenders, pipes and flowlines, valves, manifolds and pressure control devices, high-pressure high-volume pumping units, and proppant and chemical storage, many of which are brought in and mounted on specialized trucks. The water, proppant and chemicals are mixed to form fracturing fluid and then injected into the wellbore at operating pressures upwards of 15,000 PSI. The flow of fracturing fluid, oil and gas in and out of pipes in the well is controlled and regulated at the surface with a manifold, christmas tree, or frac tree structure, which is an assembly of valves, spools, and fittings. The frac tree may also provides additional features for chemical injection points, pressure relief, and pressure gauges, transducers, flowmeters, and other sensors for monitoring and measuring fracturing parameters. Fluids and gases are pumped in and out of the manifold or frac tree via multiple flexible high-pressure lines and hoses that are typically powered with configurations of ten 1,650 HHP triplex pumping units.
During the hydraulic fracturing treatment of a wellhead, the frac tree and manifold must be safely accessed by oilfield services personnel for the installation, control, operation, maintenance and removal of specialized equipment. Mounted on top of the wellhead, the frac trees and manifold structures are typically overhead and out of reach of oilfield workers and are built to heights of around fifteen feet or more. In the past, oilfield workers gained access to the frac tree with moveable vertical man lifts, boom lifts or scissor lift equipment. However, these methods of access proved unsafe due to operator error, falls, collapse, tip overs, and the inherently dangerous conditions at the oilfield. Therefore a safer means of accessing the frac tree and manifold is needed.